Sheet metal door frames offer a simple and highly cost effective alternative to conventional wood frames, and are often installed in doorways of plasterboard walls in offices and similar environments.
The state of the art in the market today is represented by a great number of more or less complicated frame constructions, where head pieces and jambs are joined together by means of a vast variety of tongue elements and slits. The tongue elements can for instance be of the kind used in tinplate toys where the tongue is guided through the slit and bent down on the rear side of the plate. The tongue elements are normally either stamped out from the frame profile, or added by welding or other means as separate parts to the frame profiles. Other known solutions may include intricate angled joint pieces onto which the head piece and jambs are fastened.
A drawback of the majority of the above-mentioned solutions is that the frames become difficult to install on-site by craftsmen. However, it is highly desirable that the frames may be easily installed even by an unskilled craftsman. An additional and no less important drawback of existing frame constructions is the complicated shape of the metal profiles, resulting in high manufacturing costs, for example in terms of expensive cutting and stamping machinery, as well as an increased number of necessary work operations. Yet another problem is that the craftsman of ten has to hold the head piece in position, or fasten it by screws, until the jambs are fixed in their vertical positions.
It is thus an object of the present invention to alleviate the above problems by providing a cheap and simple sheet metal door frame and a method of installing such a door frame in a doorway which can be performed even by unskilled craftsmen.